1. Field of the Invention
This invention relates to compositions of aluminosilicate minerals treated with large organophilic cationic surfactants such as quaternary ammonium or phosphonium compounds and a method for purifying liquids therewith.
2. Prior Art
Many industries produce large quantities of process liquids that must be purified of contaminants prior to further processing, sale, recycle or disposal. In treating aqueous systems for removal of contaminants, various grades of activated carbon or bone char impregnated with activated carbon have been widely used. Not all grades perform well in all uses, and the more effective grades tend to be rather expensive. Economic benefits could be realized by using mineral-based sorbents, but unmodified mineral sorbents do not perform well in aqueous systems, though they are known purifying agents for organic liquids, notably fats and oils. For example, fuller's earth has been a known purifying agent and decolorizer for fats and oils since antiquity.
It has been recognized that mineral substrates may be modified to obtain a more organophilic surface to be effective sorbents for certain uses. A relatively high surface area and a cationic exchange capacity above about 5 milliequivalents per 100 grams of sorbent is desirable. Exemplary mineral substrates are sepiolite, attapulgite (palygorskite) and smectites. In their naturally occurring state many of these clay minerals (aluminosilicates) swell or slake in aqueous systems resulting in gel formation or colloidal dispersions that are extremely difficult to separate from the liquid. Granular forms of these clays in naturally occurring state or condition would simply fall apart in aqueous media. Some sorptive minerals such as bauxite do not exhibit this deficiency. Clays may be rendered substantially non-gelling or non-slaking by heat treatment. By way of example attapulgite clay calcined at temperatures in the range 200.degree.-550.degree. C. is rendered non-gelling and non-slaking thereby. Reference is made to W. S. W. McCarter et al, "THERMAL ACTIVATION OF ATTAPULGUS CLAY", Industrial and Engineering Chemistry, vol. 42, pages 529-533, 1950. This treatment alone is not sufficient for the mineral to effectively remove contaminants from many contaminated aqueous liquids.
Surface modification to make the mineral surface more organophilic by placing an organic-substituted amine or quaternary ammonium compound thereon is known. The great bulk of these compositions are used in thickening and related arts and require a swelling or gelling-grade clay, e.g. montmorillonite, bentonite, hectorite and other smectites as well as attapulgite and sepiolite. In some instances these materials have shown utility as sorbents for organic molecules in aqueous systems. Reference is made to C. T. Cowan et al, "ADSORPTION BY ORGANOCLAY COMPLEXES", Clays and Clay Minerals, vol. 9, pages 459-467, 1960. Difficulties in handling these materials would preclude their use in large-scale treatment of process liquors. U.S. Pat. No. 4,167,481 to Cremers et al discloses effective removal of metal cations from wastewater by addition of certain polyamines in the presence of a cation exchanger such as natural bentonites, montmorillonites and zeolites. The metal cation is complexed by the amine and subsequently adsorbed on the aluminosilicate material.
Quaternary-treated gelling grade attapulgite is also known. Reference is made to U.S. Pat. No. 2,797,196 to Dunn and U.S. Pat. No. 2,885,360 to Haden et al, in which the treated clay is used as a thickening agent for various organic liquids.
Unmodified, heat-treated attapulgite has disclosed use in water treatment for removing certain metal cations, hormones, toxins, viral micro-organisms and pesticides. Reference is made to the following U.S. Patents to Sawyer: U.S. Pat. Nos. 4,054,515; 4,116,825; 4,116,826; 4,116,827; 4,116,828. A specially processed form of heat-treated attapulgite has disclosed use as a filter aid in U.S. Pat. No. Re. 25,464 (Oct. 15, 1963) of U.S. Pat. No. 3,080,214. A method of preparing heat-treated, so-called "activated" attapulgite which is substantially non-gelling and non-slaking is disclosed in U.S. Pat. No. 3,041,238 to Allegrini.
Heat-treated attapulgite modified by addition of amines has found use as a toxicant carrier as disclosed in U.S. Pat. No. 3,024,164 to Sawyer and as an anti-caking agent disclosed in U.S. Pat. No. 3,234,003 to Sawyer et al.
None of the above-mentioned references teaches either heat-treated non-gelling grades of attapulgite or non-gelling grades of smectite clays modified by ion exchange with an organic-substituted quaternary ammonium or phosphonium compound or the use thereof in purification of liquids, especially aqueous liquids.
An object of the present invention is to modify a sorptive mineral substrate to make it effective in purifying liquids in which activated carbon has been virtually the sole viable sorbent.
Another object of the invention is a method of purifying, decolorizing and/or removing dissolved inorganic and organic contaminants including colloidal size color bodies from aqueous liquid systems.